;THIS IS WHERE OUR DEMO BEGINS


; WLA-DX banking setup

.memorymap
defaultslot 0
slotsize $8000
slot 0 $0000
.endme

.rombankmap
bankstotal 1
banksize $8000
banks 1
.endro


; SDSC tag and SMS rom header

.sdsctag 1.10,"Background Color","SMS Color Tutorial","Stan"

.bank 0 slot 0
.org $0000

; Boot section

    di              ; disable interrupts
    im 1            ; Interrupt mode 1
    jp main         ; jump to main program

.org $0066

; Pause button handler

    ; Do nothing
    retn


; Main program

main:
    ld sp, $dff0

    
    ; Set up VDP registers
    
    ld hl,VdpData
    ld b,VdpDataEnd-VdpData
    ld c,$bf
    otir

    
    ; Clear VRAM
    
    ; 1. Set VRAM write address to 0 by outputting $4000 ORed with $0000
    ld a,$00
    out ($bf),a
    ld a,$40
    out ($bf),a
    ; 2. Output 16KB of zeroes
    ld bc, $4000    ; Counter for 16KB of VRAM
    ld a,$00        ; Value to write
    ClearVRAMLoop:
        out ($be),a ; Output to VRAM address, which is auto-incremented after each write
        dec c
        jp nz,ClearVRAMLoop
        dec b
        jp nz,ClearVRAMLoop

    
    ; Load palette
    
    ; 1. Set VRAM write address to CRAM (palette) address 0 (for palette index 0)
    ; by outputting $C000 ORed with $0000
    ld a,$00
    out ($bf),a
    ld a,$c0
    out ($bf),a
    ; 2. Output color data
    ld hl,PaletteData
    ld b,(PaletteDataEnd-PaletteData)
    ld c,$be
    otir

 
    ; Background Color
    ; THIS IS OUR ACTUAL BACKGROUND COLOR PROGRAM
    
Background: 
    ld a,$00
    out ($bf),a
    ld a,$00
    out ($bf),a
    ld a,$c4       ; Turn on the screen
    out ($bf),a
    ld a,$81
    out ($bf),a

; Data for our program to use


PaletteData:
.db $30
PaletteDataEnd:

; VDP initialisation data
VdpData:
.db $04,$80,$84,$81,$ff,$82,$ff,$85,$ff,$86,$ff,$87,$00,$88,$00,$89,$ff,$8a
VdpDataEnd:

;This background color program was built using information found
;in Maxim of SMS Power fame's original programming tutorial.
;All information concerning the setting up of the VDP before the
;actual background code is his creation and the author owes him a
;great deal of gratitude for writing it.
;Background Color Demo Copyright Stan 2009

;THIS IS THE ABSOLUTE END OF OUR PROGRAM DEMO